Having worked in the field of stormwater management for almost 20 years, and seeing the conceptual and technological development of stormwater management and BMPs, it is clear we have had successes and failures.
We need to learn from both, especially with USEPA’s national rulemaking activities to establish a program to reduce stormwater discharges and to make other regulatory improvements to strengthen its existing stormwater program.
Recent calls to manage water quantity and quality through green infrastructure have led to new and exciting approaches to stormwater management.
Currently, LID is sweeping the nation as the new conceptual approach, leading to the use and development of new decentralized BMPs of which many are not wholly understood. Rather than letting an “ahead of the curve” approach lead to failure and disappointment, we must take this opportunity to get it right.
We need to better understand the impacts of solids loading on surface and subsurface BMP’s with particular reference to land use.
Much of the field research is short-term and conducted in ideal conditions. However, the data are translated for all land use applications, many of which generate substantially higher pollutant loads. Given proper design and non-excessive loading, bio-infiltration systems can assimilate pollutants and be sustainable, however if the assimilative capacity of the system is exceeded, failure can be rapid and catastrophic. More research, including lab and long-term field, is needed to insure sustainable design.
Effective pretreatment of infiltration systems and maintenance must be mandated and enforced.
LID has led to a proliferation of underground infiltration technologies, which are classified as UICs. Typically installed underneath a parking lot, these systems are difficult to inspect and virtually not maintainable. Pretreatment is often not required or is provided by simple settling device, which may stop coarse grit, trash and debris from entering the system. However, these devices are not effective on fines, organic particulates and dissolved components that will lead to the ultimate failure of the systems.
We need to better understand BMP interactions at the site scale with modeling that includes surface water and groundwater interactions.
The original concept of LID was embedded in the understanding of a site’s hydrologic characteristics and then applying a set of BMPs either through modeling or other engineering approaches to mimic the preexisting hydrology. Unfortunately, this has morphed into a menu approach of selecting a series of BMPs without a clear understanding of how these facilities will interact with each other and function on the site as a whole.
A national level testing protocol for both manufactured and non-proprietary BMPs is critical to success.
The EPA needs to provide more guidance, funding and sanction of testing programs, and monitoring and evaluation need to extend to all BMP’s rather than just the manufactured ones. Current efforts by the ASCE EWRI, New Jersey Corporation for Advanced Technology (NJCAT) and the Water Environment Research Foundation (WERF) need to be supported and funded to ensure that BMP performance and maintenance costs are objectively understood and meeting the goals for water quantity and quality management.
EPA intends to propose a rule to strengthen the national stormwater program by June 10, 2013 and complete a final action by December 10, 2014. For more information on EPA’s proposed rule, see http://water.epa.gov/polwaste/npdes/stormwater/Proposed-National-Rulemaking-to-Strengthen-the-Stormwater-Program.cfm.